We are presented with 3668 and 7243. Let's work out the sum.

Step 1: We'll start by adding the digits 8 & 3 in column 1 and get 11.
We'll write down the last digit 1 and carry the 1 to the next column.

Step 2: We'll start by adding the digits 6 & 4 in column 2 and get 11.
We'll write down the last digit 1 and carry the 1 to the next column.

Step 3: We'll start by adding the digits 6 & 2 in column 3 and get 9.

Step 4: We'll start by adding the digits 3 & 7 in column 4 and get 10.
We'll write down the last digit 0 and carry the 1 to the next column.

So, 3668 + 7243 = 10911.

